Determination of carbonyls using liquid chromatography-mass spectrometry with atmospheric pressure chemical ionization

A liquid chromatographic method for the determination of aldehydes and keto nes based on mass spectrometric detection is described. Recently developed modular derivatizing agents are employed for analysis. These hydrazine reag ents, e.g. 4-dimethylamino-6-(4-methoxy- 1-naphthyl)-1,3,5-triazine-2-hydra zine (DMNTH), react with the carbonyl compounds with the formation of the r espective hydrazones, which are separated by HPLC-MS with atmospheric press ure chemical ionization in the positive mode. Electrospray ionization may a lso be used for analysis. Particular focus is directed on various calibrati on approaches, including external calibration with standard solutions and i nternal calibration with a hydrazone standard of cyclobutanone, an aldehyde not likely to occur in real samples. A second approach for internal calibr ation is based on the C-13(2)-labelled acetaldehyde hydrazone standard. Dif ferent calibration approaches may then be used for the analysis of real sam ples. Limits of detection range from 2 x 10(-8) to 5 x 10(-8) mol L-1 for a series of hydrazones, including hydrazones of saturated aldehydes with alk yl chain lengths from 1 to 7 carbon atoms, and hydrazones of selected unsat urated and aromatic aldehydes as well as ketone hydrazones.